Photoflash lamp



Nov. 13, 1962 w. c. FlNK ETAL 3,063,277

PHOTOFLASH LAMP Filed March 25, 1959 INVENTORS WILL/14M CF/IVK BY HflW/IRD s. PAINTER c Qo- ATTOR EY United States Patent Ofiice 3,063,277 Patented Nov. 13., 1962 3,063,277 PHOTOFLASH LAMP Will am C. Fink, Williamsport, and Howard S. Painter, Linden, Pa., assignors to Sylvania Electric Products Inc, a corporation of Delaware Filed Mar. 25, 1959, Ser. No. 801,807 9 Claims. (Cl. 67-31) This invention relates to photoflash lamps and more particularly to photoflash lamps characterized by a duratron of light emission at useful light levels many, many times longer than that of the more popular types of pros ently available commercial flash lamps.

Generally speaking, the present art of making photoflash lamps is concerned primarily with photographic flash lamps which have a high intensity light peak or a certain level of light intensity for a maximum duration of about 60 milliseconds. Such a light source usually comprises an hermetically sealed envelope, provided with a protective coating and filled with a combustion-sup porting gas and a combustible, usually in the form of shredded foil, which upon ignition, burns with a brilliant, fast flash. The ignition system usually comprises a pair of lead-in wires, a coating of ignition paste on the inner ends of the lead-in wires, and a fine tungsten filament attached to and supported by the lead-in wires near the inner ends thereof.

Although this type of photographic flash lamp has proved to be quite satisfactory for the more conventional uses, it has been found that, for certain applications, such as motion picture, and especially high speed motion picture, photography for example, a light source of useful light levels characterized by a duration of light emission of several seconds is highly desirable. In view thereof, the principal object of this invention is to provide such a flash lamp.

A feature of this invention is the structure employed to support the combustible.

The photoflash lamp of this invention is an improvement over the photoflash lamp shown and described in the co-pending application of W. C. Fink et al., Serial Number 672,157, filed July 16, 1957, now Patent No. 2,955,447, entitled Photoflash Lamp, and assigned to the same assignee as this invention. In that application, there is disclosed a flash lamp comprising a sealed transparent envelope, within which a strip of magnesium foil is supported, and which is provided with a gas filling of nitrogen and oxygen.

In accordance with the principles of this invention an improved foil-supporting structure is provided.

In the accompanying drawing illustrating a specific embodiment of the invention, FIGURE 1 is an elevational view of a photoflash lamp, partly broken away, showing one embodiment of the invention.

FIGURE 2 is a detail of the strip of foil and itssupporting structure.

FIGURE 3 is a top view of the strip of foil showing its corrugated configuration.

Referring now to the embodiment illustrated in FIG- URE 1, the photoflash lamp comprises a sealed transparent envelope 2, of glass or the like, within which a stem 4 is disposed. A pair of lead-in wires 6 are supported by and extend through the stem 4, the outer ends thereof being connected to the base 10- at 12 and 14 respectively, to provide the means through which electrical energy may be supplied to a lamp filament 16 which is attached to and supported by the lead-in wires at the inner ends thereof. The inner end of each of the lead-in wires 6 is provided with a gob of ignition paste 18 which usually contains an oxidizer, zirconium metal powder and nitrocellulose binder. The stem 4 is provided with a protective asbestos disc 19.

A strip of magnesium foil 20 is supported within the envelope 2 by a framework 22. To facilitate ignition of the strip of magnesium foil 20, the lower end thereof is preferably provided with a coating 21 comprising a mixture of zirconium metal powder and nitrocellulose binder. The framework 22 comprises a substantially U-shaped nickel wire 24 and a pair ofspaced, substantially parallel molybdenum wires 26 attached to the U-shaped nickel wire 24 substantially transversely thereof. A length of nickel wire 28 is attached to the bight 30 of the U-shaped nickel wire 24 transversely thereof. The inner wall of the top of the envelope 2 is provided with a body of a suitable cement mixture 32 within which the cross, formed by wire 28 and 'bight 30, is embedded,

thereby providing the means for supporting the frame-' work 22. The cement mixture 32 may be a mixture of equal parts by weight of an epoxy resin, such as Shell Epon #828, and a polyamid resin, such as General Mills Versamid #125, for example. The cross is embedded in the liquid cement which is then cured for about three minutes at about 140 C., thereby firmly attaching the framework 22 to the top of the lamp envelope.

In the specific embodiment of the invention, the combustible is a strip of magnesium foil 20. However, materials other than magnesium, which are well known in the art as photoflash lamp combustibles, may be used. Since the primary goal is the provision of a light source of useful light levels characterized by a duration of light emission of several seconds, we have found that best results are obtained with corrugated foil having several perforations 34 as shown in the several figures of the drawing.

Although the framework supporting structures shown in the above-identified co-pending application have proved to be satisfactory in most instances, in some cases the transverse molybdenum wires 26, from which the strip of foil 20 depends','fail to support the foil during the entire period of time required for complete combustion thereof. Since the combustion temperature runs about 2900 'C. and over, the wires 26 tend to burn off before combustion of the foil has completed.

Heretofore, it has been the practice to protect heate metal wires from burning up in an oxygen-containing atmosphere by using a ceramic coating similar to porcelain, a low-melting glass frit, or a metal silicate compound with much the metal wire is glazed or coated.

- The protective coating adheres firmly to the surface and cleaned for the necessary welding of the individual parts i if used for a supporting frame.

We have found that, contrary to expectation, a glaze adherent to the surface of the metal wire is not necessary in the long duration flash lamp, despite the concentration of oxygen therein and a combustion temperature of over 2900 C. We have found that the aforementioned disadvantages associated with the use of unprotected molybdenum support wires may be overcome by slipping over each of the molybdenum wires a sleeve of fine glass tub ing 36, such as is commonly used as an exhaust tube in the lamp manufacturing art. These sleeves 36 give additional protection to the framework 22 to secure the strip of foil 20 in a fixed position during handling and transportation of the lamp as well as during the burning of the foil. The foil is thus kept safely in its position throughout burning; it does not fall off. It gives all the usable light during the entire duration of the combustion.

In the specific embodiment of the invention illustrated in the accompanying drawing, those segments of the spasm? I 3 U-shaped nickel wire 24 lying between the transverse molybdenum wires 26 are also provided with protective sleeves of glass tubing 38. Although this arrangement enhances further the stability of the framework 22, it has been found that if the diameter of the Wire 24 is increased substantially the protective glass sleeves 38 are not necessarily needed. On the other hand, however, this alternative cannot be utilized insofar as the molybdenum support wires 26 are concerned. A molybdenum support wire of very small diameter, such as 0.015 for example, should be used to prevent as much heat conduction losses as possible. A highly eflicient light level is maintained by these means.

It will be noted that the strip of foil 20 is corrugated and is provided with a plurality of perforations. It has been found that this arrangement provides for a greater concentration of heat in a smaller area and improves the combustibility of the foil.

What we claim is:

1. In combination, a photofiash lamp envelope; a support attached to and depending from the inner wall of the photofiash lamp envelope; a wire attached to and extending transversely of said dependingsupport intermediate the ends thereof; a sleeve of glass tubing encircling said Wire; and a strip of flammable foil supported by and depending from said wire.

2. In combination, a photofiash-lamp envelope; a support attached to and depending from the inner wall of the photofiash lamp envelope; a wire attached to and extending transversely of said depending support intermediate the ends thereof; a sleeve of glass tubing encircling said wire; and a corrugated strip of flammable foil supported by and depending from said wire.

3. In combination, a photofiash lamp envelope; a support attached to and depending from the inner wall of the photofiash lamp envelope; a wire attached to and extending transversely of said depending support intermediate the ends thereof; a sleeve of glass tubing encircling said wire; and a corrugated strip of flammable foil, having a plurality of perforations, supported by and depending from said wire.

4. In combination, a photofiash lamp envelope; a substantially U-shaped support attached to and depending from the inner wall of the photofiash lamp envelope; a pair of spaced, substantially parallel wires attached to and bridging the legs of said U-shaped support transversely thereof and intermediate the ends thereof; a sleeve of glass tubing encircling each of said wires; and a strip of flammable foil supported by and depending from said wires.

5. In combination, aphotoflash lamp envelope; asubstantially U-shaped support attached to and depending from the inner wall of the photofiash-lamp envelope; a pair of spaced, substantially parallel wires attached to and bridgnig the legs of said U-shaped support transversely thereof and intermediate the ends thereof; a sleeve of glass tubing encircling each of said wires; and a strip of corrugated flammable foil supported by and dependingfrom said wires,

6. In combination, a photofiash lamp envelope; a substantially U-shaped support attached to and depending from the inner wall of the photofiash lamp envelope; a pair of spaced, substantially parallel wires attached to and bridging the legs of said U-shaped support transversely thereof and intermediate the ends thereof; a sleeve of glass tubing encircling each of said wires; and a strip of corrugated flammable foil, having a plurality of perforations, supported by and depending from said wires.

7. In combination, a photofiash lamp envelope; a substantially U-shaped support attached to and depending from the inner wall of the photofiash lamp envelope; a pair of spaced, substantially parallel wires attached to and bridging the legs of said U-shaped support transversely thereof and intermediate the ends thereof; a sleeve of glass tubing encircling each of said wires; and a sleeve of glass tubing encircling each of said legs of said U-shaped support between the points of attachment of said wires thereto; and a strip of flammable foil supported by and depending from said Wires.

8. In combination, a photofiash lamp envelope; a substantially U-shaped support attached to and depending from the inner wall of the photofiash lamp envelope; a pair of spaced; substantially parallel wires attached to and bridging the legs of said U-shaped support transversely thereof and intermediate the ends thereof; a sleeve of glass tubing encircling each of said wires; a sleeve of glass tubing encircling each of said legs of said U-shaped support between the points of attachment of said Wires thereto; and a corrugated strip of flammable foil supported by and depending from said wires.

9. In combination, a photofiash lamp envelope; a substantially U-shaped support attached to and depending from the inner wall of the photofiash lamp envelope; a pair of spaced, substantially parallel wires attached to and bridging the legs of .said U-shaped support transversely thereof and intermediate the ends thereof; a sleeve of glass tubing encircling each of said wires; a sleeve of glass tubing encircling each of said legs of said U-shaped support between the points of attachment of said wires thereto; and a corrugated strip of flammable foil, having a plurality of perforations, supported by and depending from said wires.

References Cited in the file of this patent UNITED STATES PATENTS 1,716,149 Rentschler June 4, 1929 1,971,931 Friederichsen Aug. 28, 1934 2,037,101 Van Lampt Apr. 14, 1936 2,057,583 Mey Oct. 13, 1936 2,071,369 Williams et al. Feb. 23, 1937 2,238,780 Reiter et al. Apr. 15, 1941 2,955,447 Fink et al. Oct. 11, 1960 FOREIGN PATENTS 737,594 Great Britain Sept. 28, 1955 

